In recent years, digitalization of a video signal has been increasingly proceeded, wherein a brightness signal sampling processing is adopted in processing the video signal (For example, see the Patent Document 1).
FIG. 24 is a block diagram of a brightness signal sampling processing apparatus according to a conventional technology.
A pixel skipping standard value setting unit 401 in the sampling processing apparatus in the conventional brightness signal processing apparatus is constituted as below. First, a counter 501 is reset every time when a vertical differential signal S211 is inputted. A load hold device 503 loads an output from the counter 501 based on a horizontal differential signal S210. The load hold device 503 supplies the loaded output value from the counter 501 to the counter 501 as the input of the counter 501. The counter 501 counts number of lines by counting the output value of the load hold device 503.
Next, n bits, which is number of bits corresponding to a repeated pattern of the brightness signals for skipping pixels desirably from the number of the lines outputted by the load hold device 503, are retrieved from lower-order bits and supplied to the counter 502. In the lower-order bits described here, as they are retrieved from the output of the load hold device 503, the retrieved n bits change in such manner as 0, 1, 2, 3, 0, 1, 2, 3, . . . in the case of, for example, n=2 every time when the number of the lines to be processed changes.
Next, the counter 502 counts as much as the lower-order n bits retrieved from the load hold device 503 as an initial value in accordance with a reference clock. Because the initial value supplied to the counter 502 is different with respect to each of the lines processed by as much as the lower-order n bits of the load hold device 503, a value at which the counting starts is different per line. The output of the counter 502 is a pixel skipping standard value S411.
FIG. 25 shows a conventional sampling example (an example in which the pixel skipping standard value S411 is generated). In the drawing, one square corresponds to one pixel on a display screen, and a vertical direction corresponds to lines. Referring to the pixel skipping standard value S411 in FIG. 25, the value in the first line is “00”, the value in the second line is “01” of a binary numeral, the value in the third line is “10”, the value in the fourth line is “11”, and the value in the fifth line is “00”, and a position where the counting starts is different with respect to each line. Such a circuit configuration allows the brightness signal to be sampled not only in the fixed pixels but also in the pixels in an oblique direction on the screen.                Patent Document 1: WO01/039489 (Pages 11-14, FIGS. 5-7)        